Press section



Nov. 3, 1959 L. HORNBOSTEL PRESS SECTJIION Filed Jan. 29, 1958 Fa lLloyd Horn bosfel @QTZHE United States Patent PRESS SECTION Lloyd Hombostel, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis.,jacorporation of Wisconsin I Application January 29, 1958, Serial No.711,826

1 Claims. (Cl. 162-305) through one or more suction presses, wherebymoisture 'is removed from the web by mechanical nip pressure of a pairof cooperating press rolls, together with suction exerted at the pressnip. Generally, Fourdrinier type paper making machines are designed'todry a web sufficiently'by suction while still on the forming wire sothat suction alone in a later press section is not effective to furtherdewater the web. Accordingly, the use of mechanical pressure eitheralone or in conjunction with suction is-necessary for'furtherdewatering. Press feltsiare generally used to convey the web from theforming wire to the paper machine press section, and the felts alsoserve to absorb moisture from the web in surface contact therewith.

I As will be appreciated, both the web and the felt are squeezed whenpassing through the press nip. Such squeezing serves to dewater both andthe water squeezed therefrom flows in part into the perforations in thesuction press roll at the nip. Heretofore, it has been assumed that thesuction area must be covered by felts 'alone'or by the felt and the web.The suction area in a;suction press roll extends from a'sealing stripat'the oncoming side to a sealing strip at the otfrunning side 'of thenip. The oncoming and offrunning sides being determined by the directionof travel of the felt and web. ,An' improvement in high speed pressoperation is described in Lloyd Hornbostel U.S. Patent No. 2,694,347

wherein the web is separated from the felt at both the oncoming andotfrunning sides of the suction area (which straddles'the press nip), sothat improved drying action opening'of the pores of the felt may beaccomplished both before and after the press nip.

The instantinvention is based upon diiferent concepts, which applyparticularly to certain types of press section arrangements. It has beenfound that the arrangement of Lloyd Hornbostel US. Patent No. 2,694,347may 'not be practical in certain press sections, because of theparticular type of web being handled,.or the moisture content of theweb, or the actual positioning of the press rolls. It has also beenfound that during extensive surface contact between a web and a felt,the

vfelt picks up moisture from the web and, if it is travelling on theunderside, effects an accumulation of moisturealong the bottom side ofthe felt. The instant invention is based upon this discovery and thediscovery of a suction press arrangement which is particularly useful incertain press section designs and which is particularly efiective in theremoval of excess water from the felt, 7

In the'instant invention, the felt and web are separated imrnediatelyupon leaving the nip, with the felt Patented Nov. 3, 1959 "ice however,on the oncoming side the felt urges the web up against the surface of abare press roll, so as to leave uncovered substantially the entiresuction area in the suction roll at the oncoming side of the nip. Thisresults in a sweeping effect of the air following the bottom of the weband passing in through the perforations in the suction roll at theoncoming side. This sweeping of air results in the removal of watertending toaccumulate along the bottom side of the felt, so that asubstantial amount of water is' drawn from the felt as it enters intothe press nip. It has been found that this results in unique advantagesin the operation of certain press sections, and particularly presssections wherein it is of advantage to pick up the web from'a prior nipalmost immediately after that nip with the instant felt in question. Insuch an arrangement the relatively wetweb passes from the first nip andis received immediately by the felt. This felt then carries the Web intothe suction press of the instant invention.

It is, therefore, an important object of the instant invention toprovide an improved suction press.

It is a further object of the instant invention to provide an improvedpaper machine suction press comprising a pair ofpress rolls defining apress nip therebetween, at least one of said rolls being a suction 'rollhaving a suction area straddling said nip, and a looped felt lappingsaid suction roll, said felt being separated from the suction rollsurface to permit air to sweep between the felt and the suction rollimmediately before the nip and after the oncoming limit of the suctionarea.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

. and

Figure 2 is a fragmentary detail elevational view with parts broken awayand parts shown in section of a press nip and its immediate environmentfor the suction press of the instant invention. A

As shown on the drawings:

In Figure 1, the reference numeral 10 indicates generally a papermachine comprising a looped forming wire 11 whereon a web W is formedand the forming wire 11 travels over a suction roll 12, which is a couchroll with suction area 12a; and the wire 11 passes around a turning roll13 to reverse the direction thereof.

In the machine 10, there is provided a looped pickup felt 14, a suctionpickup r011 15 (With suction area 15a and save-all pan 1512) within theloop of the pickup felt 14 urging the pickup felt 14 against the web Won the forming wire 11 to transfer the web W to the underside of pickupfelt 14, and a guide roll 16 within the loop of the pickup felt 14 andcooperating with the suction pickup roll 15 to define a downwardlyinclined reach 14a of the pickup felt 14. The guide roll 16 is providedwith a suction area 16a for retaining the web W upon the felt 14 as itis reversed around the guide roll 16.

Above the guide roll 16 there is positioned a reverse press, indicatedgenerally by the reference numeral P, comprising a first suction pressroll 17 presenting a suction area 1711 within the loop of the pickupfelt 14, a plane surfaced or bare roll 18 defining a first press nipN-.-1 with the first suction press roll 17, a press felt 19,

a second suction press roll 20 with a suction area 20a within the loopof the press felt 19 defining a second press nip N-2 with the planesurfaced roll 18. The press nip N-1 extends generally upwardly and isaligned angularly with respect to the first 'fel't reach 14a of the felt14. The suction area 17a extends from the oncoming side to just aboutthe main nip or pressure area for the nip 'N1. The web W is transferredat the nip N,1 onto .he bare roll surface and on this surface the web 'Wremains as it passes through the second nip vN-2. At the second nip N-2,the suction area is arranged (in accordance with the principle ofHornbostel US. Patent No. 2,694,347) in that the suction area 20astraddles the press nip N-2 and the press felt 19 covers the entiresuction area 20a, but is itself uncovered by the web for the greaterportion of its travel at both the oncoming and oifrunning sides of thenip N-2.

Nextin Figure 1, there is shown an upper plane roll 21 and a lowersuction roll 22, with suction area 22a, defining a press nip N3. If anattempt is made to feed the web W directly from the second nip N-2 tothe third nip N-3, without the support of a felt, there is a tendencyfor the web to waver in its course of travel, and this may lead tobreaks in the web at this area. Accordingly, it is particularlyadvantageous to pass the web W beneath a small guide roll 23 which urgesthe web W against the top side of a press felt 24 at or near a felt roll25. The press felt 24 is urged gently against the web W at the roll 23.The rolls 23 and 25 are mounted immediately after the nip N-2, so thatthe .web W may pass therethrough without the slightest waver in its"travel. It may be mentioned also that a doctor D is mounted on the bareroll 18 for the usual purposes inkeeping the roll 18 clean and also forhandling of broke during startup. The web W is thus taken from thesurface of the bare roll 18 prior to the doctor D and passed between therolls 23 and 25. Thereafter, the web W is carried by the felt 24 intothe nip N-3.

As will be noted from Figure l, the felt 24 turns around a guide roll 26at the oifrunning side of the nip N-3 so that the felt covers the entireoffrunningside of the suction area 22a, but is uncovered by the Web Wduring most of its run on the ofirunning side of the suction area 220,because the web W is guided away by a roll 27 (and by its naturaltendency to adhere to the bare roll surface 21). Thisfeature of thearrangementfor the press rolls 21 and 22 is similar to that described inHornbostel US. Patent No. 2,694,347, and will also be brought out inFigure 2 of the instant description. 1

Referring now to Figure-2, it will be seen that thebare roll 21 carriesthe web W away from the nip N3,immediately after pressure is relieved atthe nip N-3, so that the felt 24 covering the offrunning suction area isuncovered by the web during the majority of its travel at the offrunningside of the nip N-3.

As is indicated the nip pressure is applied during an area expressed bythe angle A shown in Figure 2, and the felt 24 is uncovered by the web Wat the ofirunning side through an angle'B. The angle B is greater thanthe angle A. The suction area 22a for the suction roll 22 extends, asshown in Figure 2, from an oncoming limit defined by the oncomingsealing strip 22b to an offrunning limit-defined by the offrunningsealing strip 22c. -In actual practice, the olfrunning area B is two toten times greater than the nip area A and the oncoming area C is ofsubstantially smaller size than A or B.

An important feature here, however, is that the oncoming area C of thesuction roll 22 is not covered by either the felt 24 or the combinationof the felt and the web W. Instead, the suction area C is substantiallyun- .covered by both the felt 24 and the web W. Theweb W is urged bythe. felt 24 against the bare roll 21 at the oncoming side. During thetravel of the felt 24 from the initial guide rolls 23, 25 of Figure 1 tothe nipN- 3, a--substantial amount of water is picked up by the felt 24from the web W. Since the felt 24 is beneath the web W, there is atendency for loose water to accumulate at the underside of the felt 24.This water would otherwise be forced back into the web W and the felt 24at a press nip, if it were not for the present arrangement, whichpermits air to sweep beneath the felt 24 and into the oncoming area C ofthe suction area 22a. The sweeping of air tends to move loose water fromthe bottom of the felt 24 and also to open up the bottom portion of thefelt 24 and even draw water therefrom. In this way, the felt 24 has hadan additional drying effect imparted thereto prior to the nip N-3, sothat it will not tend to force water back into the web W at the nip N-3.Instead, the water will tend to flow primarily from the web W throughthe felt 24 and into the shell perforations 22d at the nip area A.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

I claim as my invention:

1. A paper machine suction press comprising a .pair of press rollsdefining a press nip therebetween, at least one of said rolls being asuction roll having a suction area straddling said nip, and a loopedfelt lapping said suction roll, said felt being separated from thesuction roll surface to permit air to sweep between the felt and thesuction roll immediately before the nip and after the oncoming limit ofthe suction area, said felt further covering the offrunning side of saidsuction area.

2. In a paper machine, a bare press roll, a suction press roll defininga press nip therewith, said suction roll having a suction areastraddling said nip, a looped press felt lapping said suction roll andcarrying a paper web through said nip, and guide means for the feltseparating the felt from the suction roll immediately before thenip andafter the oncoming limit of the suction area, said felt further coveringthe oifrunning side of said suction area.

3. A paper machine suction press comprising a pair of press rollsdefining a press nip therebetween lying in a plane generally tangentialto booth said rolls, at least one of said rolls being a suction rollhaving a suction area straddling said nip, a looped felt lapping saidsuction roll, saidfelt being separated fromthe suction roll surface topermit air to sweep between the felt and the suction roll immediatelybefore the nip and after the oncoming limit of the suction area, saidfelt covering the offrunning side of the suction area completely, andweb guide means mountedon the side of said plane opposite said suctionroll to maintain the felt uncovered for most of its run over the suctionarea at the offrunning side.

4. A paper machine comprising a first pair of'press rolls defining afirst press nip.therebet ween, meansfeeding a web through said firstnip, a second pair of press rolls defining a second press nipftherebetween, at least one of said second pair of press rolls being asuction roll having a suction area straddling said second nip, and alooped felt receiving the web at the ofirunning side of said first nipand lapping the suction roll to feed the web through the, second nip,said felt being separated from the suction roll surfaceto permit air tosweep between the felt and the suction roll'immediately before the nipand after the oncoming limit of the suction area.

5. A paper machine comprising a first bare roll, a first suction rolldefining a first nip therewith, a second bare roll, a second suctionroll defining a second trip therewith, each suction roll having asuction area straddling its nip, a first felt feeding a web through thefirst nip and covering the entire suction area of the first suctionroll, means maintaining the first felt uncovered by the web for most ofits run on both the oncoming and olfrunning sides of the first suctionarea, and second :felt receiving the web fro'mthe first nip and feedingthe web into the second nip, said second felt being separated from thesurface of the second suction roll to permit air to sweep between thefelt and the suction roll immediately before the nip and after theoncoming limit of the suction area.

6. A paper machine suction press, comprising a bare roll and a suctionroll defining therebetween a nip, and a looped press felt lying againstthe bare roll in advance of the nip and against the suction roll afterthe nip.

7. A paper machine suction press, comprising a bare roll and a suctionroll defining therebetween a nip, and a looped press felt lying againstthe bare roll in advance of the nip and against the suction roll afterReferences Cited in the file of this patent UNITED STATES PATENTS1,905,911 Kellett Apr. 25, 1933 2,083,818 Berry (1) June 15, 19372,204,426 Millspaugh June 11, 1940 2,209,578 Berry (2) July 30, 19402,764,917 Niks Oct. 2, 1956

